Ari,
Usually the creator of the vector data would select a
map scale (e.g. 1:50,000) that the vectors would be
rendered, then ensure the positional accuracy and the
resolution/point-density of the vectors would be suitable
for that scale. Of course the end user of the data may
choose to use it at a different scale, but it may appear too
generalized (jaggy, lack points, etc) at a larger scale
(e.g. 1:10,000), or have too many points (or features) at
smaller scale (1:1,000,000).
For raster image data (sorry, I don't have one for
vectors), my rule-of-thumb for relating resolution to scale
is: take the pixel size (resolution) in meters, multiply by
4000 and that will give a reasonable scale to view the
image. So for Quickbird satellite image data with a
resolution of 0.6 meters, a good scale would be 1:2,400 (0.6
x 4000=2400). Any larger scale than that and you'll start
to see pixel edges.
For vectors, perhaps a roughness value (using fractal
math?) could be computed and used with the coordinate values
to come up with appropriate scale. It would likely depend
on the objects the vectors represented (streams are rougher
than roads, etc). Just a thought...
Brent Fraser
GeoAnalytic Inc.
Calgary, Alberta
----- Original Message -----
From: "Ari Jolma" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, May 08, 2007 3:35 AM
Subject: [Geowanking] Scale of vector data
> I'm a bit ignorant on this issue. I've thought that it's a
bit
> meaningless to talk about the scale of vector data but
clearly one can
> have more accurate and less accurate polygons for example.
>
> Are there commonly accepted methods for computing the
scale of an
> arbitrary geospatial dataset?
>
> Just asking,
>
> Ari
>
> --
> Prof. Ari Jolma
> Geoinformaatio- ja paikannustekniikka / Geoinformation and
positioning
> Teknillinen Korkeakoulu / Helsinki University of
Technology
> tel: +358 9 451 3886 address: POBox 1200, 02015 TKK,
Finland
> Email: ari.jolma at tkk.fi URL: http://www.tkk.fi/~jolma
>
>
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